BR112017024003B1 - abrasive belt - Google Patents

Abstract

The present invention relates to an abrasive belt which comprises a textile fabric being formed from interconnected fabric strands, and a coherent abrasive area formed on one side of the textile fabric, wherein the abrasive belt further comprises a plurality of regularly distributed openings in the hole shapes from side to side. The abrasive belt in accordance with the present invention makes it possible for a homogeneous distribution of the abrasive material and, consequently, for a uniform sanding finish, as well as for an appropriate dust removal and for suitable mechanical properties.

Description

TECHNICAL FIELD

[0001] The present invention generally refers to abrasive products, in the form of abrasive belts (abrasive belts), abrasive belt grinding products or corresponding forms of conversion.

FUNDAMENTALS OF THE INVENTION

[0002] Abrasive belts (abrasive belts) belong to the category of abrasive products having extensive use both in portable devices (manuals) and in stationary devices of various projects (designs) and in different configurations (installations) where the advantage is the that an endless and homogeneous abrasive area can be used for grinding, sanding, finishing or polishing metal, paint, plastic and wood, as well as lacquered surfaces and so on.

[0003] The back parts of abrasive belts are typically paper or fabric and should fulfill certain requirements considering their mechanical properties and functionality. Longitudinal elongation needs to be kept low and strength in the transverse direction should be sufficient for effective (real) product applications.

[0004] Applications for abrasive belts are in most cases related to excessive dust formation, and a limiting issue in the use of this type of abrasive is clogging when the formed dust and other particles are not removed from the area of work. Removal of dust and other particles is hampered (prevented) if the backside material has a closed surface. Especially sanding materials such as wood, plastics and paints rich in filler (swelling) create a high amount of dust and the use of traditional belt products with closed back fabric and woven paper materials presents a significant disadvantage.

[0005] As much as the use of abrasive belts generally provides a high abrasion rate and good sanding performance, this will result in a tendency to clog and overheat. In the worst situations, this could lead to burn marks on the sanded material and to significantly deteriorate the abrasion result. Secondary disadvantageous effects are impaired working conditions, shortened service life of abrasives and, accordingly, also an increased need for maintenance interruptions.

[0006] The current state of the art is to remove the dust formed by using a dust extraction device which is positioned close to the edge of the sanding area in order to remove as much of the dust as possible. Commonly used are also devices which blow compressed air or a cleaning gas onto the belt surface and extract the particles from the belt surface by means of a vacuum extraction or the like.

[0007] It is not possible to extract dust directly through the sanding belt with such a configuration as much as conventional sanding belts with a closed structure are used. This applies to abrasive belts having a woven fabric, paper or film (film) on the back. Simply providing these belts with holes from side to side will in most cases not be effective as, at the same time, certain mechanical requirements must be satisfied. Accordingly, no more than a very limited number of holes can be implemented for the paper, woven fabric or backing film without causing a drastic and unwanted reduction in the tensile strength and durability of the belt. As a result, perforations are limited in size and number and perforated belts made from these backside materials generally do not provide efficient dust extraction.

[0008] Clogging due to the fact of grinding dust enrichment is a primary problem in the use of most abrasive products in general, but especially in sanding materials such as wood, plastics and filler-rich paints. Sanding these materials does not create a high amount of dust when using traditional belt products with woven fabric and paper backing materials.

[0009] Specifically, considering dust removal, US patent application number US 2005/020190 and US patent number US 6,923,840 describe abrasive products with open cell backings. However, as the open foam structure is tied to a continuous backing film, dust will accumulate at the openings. In European patent number EP 1,733,844, holes are created in the abrasive backside material. While these approaches will allow greater amounts of dust to accumulate in holes or openings, after a certain amount of time these areas will as well inevitably clog.

[0010] US patent number US 2,984,052 describes a woven fabric with regularly woven strands having an abrasive coating. However, abrasive areas are limited to regularly distributed bulges or islands. Such a structure is not suitable for abrasive belt applications as the evenly distributed islands will result in a certain stripe-like pattern of the sanded surface. This might be desired on some specific products, but in most sanding applications, a finish with an evenly sanded surface is of utmost importance.

[0011] The same behavior applies for a belt that is made from a textile backing, such as, for example, the abrasive described in European patent number EP 0.779,851. The described zigzag structure of knit-based bundles in the running direction is not interconnected across the belt by other surfaces covered with abrasive particles. In other words, there are “empty” areas across the belt where the connecting wires between the bundles are located below the bundles covered with abrasive particles. This will result in an abrasive effect only from the knit-based bundles that are in contact with the surface. Consequently, knitting-based bundles can induce a structure on the surface. A similar effect can occur if the pressure applied to the belt support backing is unevenly distributed over the sanded surface.

[0012] Another way to improve the removal of dust is to use or even increase the height differences on the surface of the abrasive material. This can be achieved by arranging the grain materials in a structured manner, for example in the form of dots or islands as in European patent number EP 2,390,056. If transferred to an abrasive belt, such an approach will however lead to an uneven sanding finish. What's more, the inter-island areas will clog up after a while as well.

[0013] US patent number US 5,674,122 describes an abrasive sieve (screen) intended for abrasive discs and sheets with a patterned arrangement of a plurality of openings at the back. The posterior part characteristically has distinct zones with different surface areas. Accordingly, through the abrasive product, this should result in an inhomogeneous grain distribution on the surface. Consequently, if this inhomogeneous grain distribution pattern is used in an abrasive belt product, streaks on the sanded surface should result.

[0014] Another example of an open abrasive structure is provided in European patent number EP 1.522,386 where an abrasive product comprising two layers of parallel wires running both in the grinding direction and in the transverse direction is presented. This solution is functional, but when pressure is applied to the construction, the warp yarns will lead to an uneven sanding pressure distribution over the weft yarns which are covered with abrasive particles and therefore lead to surface structuring. sanded.

[0015] In European patent number EP 0,779,851 describes an open mesh (net) fabric of interwoven or knitted yarns equipped with abrasive particles. The present invention relates more specifically to a structure based on abrasive loops or wires distributed on the surface. The concept of the present invention makes it possible for grinding dust to be removed, but the surface structure of the abrasive article is rough and the abrasive areas are located similar to spots. The construction of the abrasive material is also related to problems with mechanical strength, which should not make the product suitable for belt applications.

[0016] For abrasive belts the requirements regarding dust removal conflict with the need to modify the backside material in order to achieve the desired mechanical properties. Sufficient stiffness is, for example, achieved by impregnation with suitable resins as, for example, in US patent number US 4,386,943. Sufficient mechanical strength was also claimed to be achieved in US patent number US 5,700,188 by applying a multilayer construction.

SUMMARY OF THE PRESENT INVENTION

[0017] It is an object of the present invention to provide an abrasive belt grinding product having improved grinding performance and excellent durability.

[0018] The purpose of the present invention is solved with the abrasive belt in accordance with the accompanying independent patent claims. The other accompanying dependent patent claims define preferred embodiments, in which all of these embodiments are intended to be combinable with each other, so long as they do not contradict each other.

[0019] In particular, an abrasive belt comprises a textile fabric formed from interconnected fabric strands, and a coherent abrasive area formed on one side of the textile fabric. Additionally, the abrasive belt comprises a plurality of regularly distributed openings in the form of holes from side to side.

[0020] As a result, the term "interconnected" fabric threads comes to mean that the fabric threads at least cross one another at the points of interconnection. Preferably, the interconnect is formed in the form of tangles when one fabric yarn is looped around another fabric yarn and vice versa.

[0021] The term "coherent" means that the abrasive belt comprises a single, interconnected abrasive area that is continuous - in contrast to isolated abrasive stretches or islands. Abrasive area in this context symbolizes an area with which a workpiece can be sanded or ground (worn out). The term “fabric threads” refers to the threads that form the basis of the textile fabric. Preferred textile fabrics are defined in the ISO 8388 standard and comprise jersey-based knitted (knitted) weft fabrics, jersey-based double-layer knitted weft fabrics, stria-based knitted weft fabrics, weft-based knitted weft fabrics, jersey-based knitted warp fabrics, jersey-based double-layer knitted warp fabrics, rib-based knitted warp fabrics, welt-based knitted warp fabrics, jersey-based knitted warp and weft blended fabrics, and others . In addition, woven fabrics are conceivable.

[0022] Due to the fact the holes from side to side, sanding dust and other particles can easily penetrate through the abrasive belt. This considerably facilitates the removal of dust from the sanding area where the workpiece is machined and prevents clogging of the abrasive belt. This, in turn, extends the lifetime of the abrasive belt and prevents overheating of the sanding surface which ensures a high quality sanding finish. Furthermore, the provision of the holes from side to side enables an operator to look through the abrasive belt when the abrasive belt is pulled to circulate. This enables the operator to have better control of the grinding process, which is particularly important for machines where grinding pressure is applied manually. Also for automatic sanding machines, this feature is advantageous, however, as it allows for visual quality control during the sanding process.

[0023] The coherent abrasive area ensures a uniform finish of the sanded product such that, due to the coherent abrasive area, there are no isolated patches across the entire abrasive belt that could show up as streaks on the sanded surface. The even distribution of the openings additionally contributes to an optimized surface finish on the sanded workpiece. On the one hand, an even distribution of openings means that the area between adjacent openings is substantially constant across the entire abrasive belt, which is equivalent to the notion that also the area density of the abrasive areas is substantially constant throughout the entire abrasive belt. abrasive belt. On the other hand, an even distribution of holes from side to side rules out that there will be local variations in the number of holes from side to side, which could lead to a non-uniform sanding result. In this regard, "area density" is an illustrative term that can be conceived as the local quotient of the area occupied by the abrasives in a given part of the abrasive belt over the (along) the virtual total area of the abrasive belt in that part ( that is, the area including the holes). Of course, this setting is only sensitive if the part is dimensioned to have a length that is at least twice the long dimension of the openings.

[0024] At the same time, the textile fabric being formed from interconnected fabric strands ensures that the abrasive belt has sufficient mechanical properties that are required for abrasive belt applications. In particular, by using a textile fabric being formed from interconnected fabric strands, holes from side to side can be formed in the abrasive belt while the longitudinal elongation can be kept low and a certain strength in the transverse direction can be achieved.

[0025] This is not only applicable for an abrasive belt, but for any grinding product suitable for unidirectional grinding operations in which an abrasive material extends along a vertical or horizontal geometric axis in order to create a surface area evenly sanded after the abrasion process. Typically the cast form of such a grinding product takes the form of a belt, but it may also be in the form of rollers, sheets, triangular shapes, discs or other suitable cast forms.

[0026] Preferably, the openings are arranged in lines perpendicular to the machine direction of the belt, wherein the openings are regularly spaced in the line direction and the lines are offset from each other with respect to the position of their openings.

[0027] The machine direction is the direction in which the belt is pulled to circulate, when used in a sander or the like. If the abrasive product is used in a different form of conversion, such as a roller, sheet or the like, machine direction can also be conceived as the direction in which the abrasive process is carried out when using the material.

[0028] The even spacing of the openings in the line direction ensures that an even sanding surface is achieved in the width direction of the sanding area. If the lines are misaligned from each other with respect to the position of their openings, the openings are not arranged in uniform rows along the machine direction. This additionally reduces the occurrence of streaks across the width of the sanding area.

[0029] As a consequence of this, it is further preferred that subsequent lines (i.e. lines that follow each other in the machine direction) are offset from each other with respect to the position of their openings.

[0030] In this regard, it is additionally preferable that the misalignment between subsequent rows is such that the openings of each second row align in the machine direction.

[0031] If viewed in the machine direction, the latter means, in other words, that an abrasive coated region between two adjacent openings in a row is followed by an opening of the next row which is again followed by an abrasive coated region of the second next line and so on. Accordingly, this arrangement effectively suppresses streaking in the finished product. Furthermore, through the entire abrasive belt integrity, a constant local abrasive area density is achieved over length scales on the order of twice the long dimension of the openings. This is equivalent to the notion that a highly homogeneous abrasive area is provided which additionally contributes to a uniform sanding finish. In addition, also from the point of view of mechanical stability of the abrasive belt, the alternating arrangement of openings contributes to an improved strength both in the longitudinal and in the transverse direction of the abrasive belt, as the following symmetrical structure ( subsequent) of the abrasive belt can absorb and distribute the forces in an optimal way.

[0032] Preferably, the abrasive belt has a uniform thickness. Uniform thickness can ensure that a contact surface for a workpiece will be as uniform as possible if the abrasive belt is pressed onto the workpiece. In addition, this makes it possible to directly control the pressure with which the abrasive belt is applied over the workpiece.

[0033] Preferably, the coherent abrasive area on one side (i.e. the front) of the textile fabric comprises a coating on one side of the textile fabric.

[0034] The coating provides a uniform base layer on top of which abrasives can be applied. As a result, the coating can even out height irregularities and additionally promote a uniform abrasive area. For this purpose, the coating can be specifically treated ("flattened") before applying the abrasive particles to form a uniform surface. As described in international patent application number WO 2014/037034, this can be achieved in a specific manner of application of the coating, for example by using a coating roller. Furthermore, a planing effect can be achieved by pressing a planing device against the as yet uncured coating. In addition, there is the possibility of abrading or mechanically grinding the readily applied coating in order to level out (flatten) any existing irregularities.

[0035] The other side of the abrasive belt (ie the back) may be substantially free of coating. On the one hand, this makes it possible to reduce the amount of coating needed to manufacture the abrasive belt and, consequently, contributes to a more cost-effective product. On the other hand, as the other side of the textile fabric is substantially free of the coating, the resulting product is more flexible. During use, this can be beneficial especially if the traction rollers around the abrasive belts are wound having small diameters. It should be noted that "substantially free from coating" does not preclude the fabric threads from carrying other materials that are, for example, part of an impregnation of the textile fabric.

[0036] Alternatively/additionally, the abrasive belt may also comprise a coating which is applied over the other side (i.e. the back) of textile fabric. Hereinafter, this coating may also be referred to as a "second coating". As a result, the second coating can be used to further refine (improve) the mechanical properties of the abrasive belt. In addition, it could be used to provide a flat backside of the abrasive belt. For some applications, a flat backing of the abrasive belt should additionally provide a uniform sanding finish, especially if high sanding pressures are applied or a sanding process is carried out in close proximity to the sanding machine's pull feature. In addition, this decreases abrasive wear in the abrasive area.

[0037] In this regard, it is additionally conceivable that the back of the belt will be flattened. As in the case of facing over the front, such flattening can be achieved by pressing, calendering or abrasion processes. As a result, such processes can either be applied directly to the textile fabric forming the back of the belt or to the second coating, if present.

[0038] Preferably, the ratio of the volume of the fabric threads to the volume of the product as a whole, not including the openings, is from 0.1 to 0.9 and even more preferably from 0.4 to 0.8.

[0039] Within this volume ratio, an abrasive product with good mechanical and topological properties can be realized. On the one hand, the resulting product has sufficient mechanical strength to withstand tensile forces in grinding applications. On the other hand, with the proportion in volume determined, it is readily possible to equalize irregularities in the height profiles of the product that arise from the interconnection points of the fabric threads. Additionally, the product can be manufactured in a cost-effective manner.

[0040] Preferably, the weight ratio between yarn and the product as a whole is from 0.2 to 0.9.

[0041] Also in terms of this weight ratio, a good compromise between mechanical and structural properties can be achieved.

[0042] With respect to the textile fabric, it is preferable that the fabric threads come to be interconnected by being knitted (knitted), sewn or interwoven.

These techniques provide a possibility to optimally satisfy the conflicting requirements of having an open structure with a preferably highly regular pattern of openings and yet, at the same time, a sufficient resistance of the belt/textile fabric against tensile forces. Furthermore, these techniques present a cost-effective way of manufacturing textile fabric.

[0044] Preferably, the openings are uniform (in size and configuration), which is beneficial in achieving a uniform (level) sanding finish.

[0045] Preferably, the openings are shaped like an equilateral quadrilateral or are of hexagonal configuration.

[0046] Being the quadrilateral openings equilateral or hexagonal in configuration is equivalent to the notion that the openings are highly symmetrical. This is beneficial in terms of the grinding result as the regions between adjacent openings are highly regular across the entire abrasive belt. In addition, these configurations can contribute to an enhanced tensile strength of the abrasive belt, as tensile forces can generally be more evenly distributed.

[0047] Preferably, the openings have a long dimension (which is, in other words, the longest diameter of the opening through the opening) and a short dimension (which is, in other words, the shortest diameter through the opening ), where the long dimension extends in the machine direction of the abrasive belt.

[0048] This feature, which in other words means that the openings are stretched in the machine direction, additionally contributes to an improved resistance of the abrasive belts against stretching along the machine direction. This can be attributed to the elongated geometry of the structure, which is capable of absorbing tension forces without inducing lateral contraction.

[0049] Preferably, the long dimension of the openings is between 0.3 mm and 20.0 mm.

[0050] These dimensions generally offer a good compromise between the mechanical strength of the abrasive belt and a sufficient size of the openings such that sanding dust and other particles can easily penetrate through the abrasive belt. Of course, the values can be adapted to the application of interest.

[0051] Preferably, the average width of the openings (i.e. the diameter of the openings in a direction perpendicular to the machine direction) is at least 0.3 times the shortest distance separating neighboring openings in a direction perpendicular to the machine steering. More preferably, the average width of the openings (i.e. the diameter of the openings in a direction perpendicular to the machine direction) is at least 0.7 times the shortest distance separating neighboring openings in a direction perpendicular to the direction of machine, and even more preferably, the average width of the openings (i.e. the diameter of the openings in a direction perpendicular to the machine direction) is between 0.8 times to 1.2 times the shortest distance separating neighboring openings in a direction perpendicular to the machine direction.

[0052] If, in other words, the width of the openings in a transverse direction (that is, a direction perpendicular to the machine direction) is of the order of a connection region in transverse direction, the probability that streaks will occur on the sanded workpiece can be further reduced. This is due to the fact that, with such dimensions, good overlapping of subsequent openings can be achieved in the machine direction, which additionally reduces the probability of streaking.

[0053] Preferably, the interconnected fabric strands are arranged in the form of bundles of a plurality of interconnected fabric strands, wherein the bundles separate neighboring openings and are arranged in such a way that they extend in a direction intercepting the direction. of machine.

[0054] Bundles are, in other words, strands of interconnected fabric threads. In accordance with this, a beam reflects the global propagation direction of the interconnected fabric strands through the textile fabric, in the sense that small local deviations in the direction of the fabric strands, arising, for example, from loops or circuits ( loops) of fabric yarns around neighboring fabric yarns not taken into account for the overall propagation direction. Accordingly, the bundles are the regions of the belt that are coated with abrasives and hence form the basis for the abrasive area. Due to the fact that the beams extend in one direction intersecting the machine direction (meaning they do not propagate strictly parallel to the machine direction), the probability of streaks on the sanded product can be further decreased.

[0055] Preferably, the number of fabric strands intersecting at interconnecting points of the interconnected fabric strands is constant throughout the abrasive belt. More preferably, the number of fabric strands intersecting at interconnecting points of the interconnected fabric strands is between two and ten.

[0056] In this regard, it is observed that, on the one hand, the formation of interconnections of fabric threads is preferable in order to produce a coherent and physically stable material. Without interconnecting the fabric yarns, only loose yarn products but no textile fabric should be created. On the other hand, interconnecting points (where fabric threads cross) necessarily entail a local height variation (ie, a point where fabric threads are locally enriched). This is potentially disadvantageous for sanding applications as interconnecting points could show streaks in the finished product. If the number of fabric strands crossing at interconnecting points is kept constant, and even more preferable, at its minimum of two strands throughout the entire abrasive belt integrity, however, height variations can be kept to a minimum. Accordingly, a highly uniform thickness of the abrasive belt can be achieved, which allows for a uniform (level) sanding finish.

[0057] Preferably, the thickness of fabric yarns is from 5 dtex to 4000 dtex and in particular from 150 dtex to 900 dtex.

[0058] Preferably, the textile fabric has an atlas or cord structure.

[0059] As a result, atlas or bead structures are suitable for combining the desired open structure of the abrasive belt with the requirement to have a uniform and coherent abrasive area. In addition, these structures allow the formation of a textile fabric that can, at least to some extent, resist strain deformation both in the longitudinal and transverse directions without excessively stretching.

[0060] Preferably, the abrasive belt additionally comprises reinforcing yarns worked into the textile fabric.

[0061] With the reinforcing wires, the mechanical stability of the abrasive belt can be further enhanced. As these reinforcing yarns are worked into the textile fabric, they affect the uniformity of the abrasive area as little as possible.

[0062] Preferably, the reinforcing yarns are worked into the textile fabric in the form of a pillar stitch.

[0063] As a consequence of this, the pillar stitch provides a possibility of arranging the reinforcement threads in directions essentially following the machine direction, which specifically strengthens the resistance of the abrasive belt against tensile forces in the machine direction. Furthermore, the abutment point is effective with respect to achieving a desired mechanical reinforcement without considerably deteriorating the uniformity (regularity) of the abrasive area.

Preferably, the reinforcement threads have a thickness of 1 times up to 1/20 times the thickness of the fabric threads and more preferably have a thickness of 1/2 times up to 1/10 times the thickness of the fabric threads.

[0065] This ensures that the reinforcing yarns will not lead to sharp rises in the textile fabric when being worked into the textile fabric. Accordingly, an abrasive belt can be obtained which is mechanically stable and at the same time has a uniform thickness.

[0066] Preferably, the reinforcing yarns are worked into or follow the bundles of the plurality of interconnected fabric yarns.

[0067] This enables the reinforcement wires not to intercept the openings, meaning that provision of the reinforcement wires does not adversely affect the open structure of the abrasive belt. Although being mechanically reinforced, the desired permeability of the abrasive belt to sanding dust and other particles can still be guaranteed.

[0068] Preferably, the textile fabric is impregnated with an impregnation, wherein, even more preferably, the textile fabric is tensioned when applying and/or curing the impregnation.

[0069] With the aid of an impregnation, the mechanical stability of the abrasive belt and in particular the strength of the abrasive belt with respect to elongations in the longitudinal direction and in the transverse direction with respect to the mechanical direction can be further improved. Additionally, if the textile fabric is tensioned while applying the impregnation, the openings in the textile fabric can be made into desired configurations before being secured by the cured impregnation. This makes it possible to delineate the configuration of the openings for the respective application. Furthermore, if the textile fabric is tensioned in the machine direction before applying the impregnation, this additionally reduces the elongation of the finished abrasive belt in the machine direction.

[0070] Preferably, the total surface area of the openings is 0.1 times to 10 times the total surface area of the total coherent abrasive area, even more preferably equal to or greater than the total surface area of the coherent abrasive area total, and even more preferably from 1.0 times to 2.2 times the total surface area of the total coherent abrasive area.

[0071] In other words, this means that it is preferred if it has a highly open structure that allows sanding dust to easily penetrate through the abrasive belt. Furthermore, this ratio between the areas of the openings and the abrasive area ensures that the fraction area of the abrasive area is evenly distributed over (along) the entire surface of the abrasive belt and that there is in particular no tendency to that certain abrasive regions will form streaks if the abrasive belt is pulled to circulate. In addition, this facilitates handling of the abrasive belt during use as an operator of a sanding machine can look through the abrasive belt, which is pulled to circulate, in order to control and/or adjust the sanding process.

[0072] Preferably, when a force of 100 N per 50 mm wide of a sample length of 200 mm is applied, the elongation of the abrasive belt is less than 1% and preferably less than 0.8%.

[0073] Additionally, in accordance with another aspect of the present invention, an abrasive belt is provided comprising a plurality of openings in the form of holes from side to side, wherein the openings are arranged in lines perpendicular to the machine direction of the belt. abrasive, the openings are regularly spaced along the direction of the lines and subsequent lines are misaligned from each other with respect to the position of their openings.

[0074] In accordance with yet another aspect of the present invention, an abrasive belt is provided which comprises a textile fabric being formed of interconnected fabric strands, a plurality of apertures in the form of holes from side to side, an abrasive area over the front of the textile fabric, and a coating on the back of the textile fabric.

[0075] Preferably, the coating on the back is flattened.

[0076] The characteristics as recited above are not only applicable for an abrasive belt, but, in general, for grinding products, in which the abrasive process is unidirectional (i.e., in which the grinding process is predominantly carried out along a direction of the grinding product) and the grinding result should be as uniform (even) as possible. Parallel to belt grinding products, possible forms of conversion include rollers, sheets, triangular configurations or discs.

BRIEF DESCRIPTION OF THE DRAWINGS OF THE PRESENT INVENTION

[0077] The present invention will be better understood, and in greater detail, by reference to the description given below by way of preferred embodiments thereof, and in conjunction with the accompanying Drawings of the Figures. In the accompanying Figure Drawings: Figure 1 schematically shows a section of an abrasive belt at different stages of the abrasive belt production process in accordance with an embodiment of the present invention; Figure 2 schematically shows a cross section of the abrasive belt in accordance with a preferred embodiment of the present invention; Figure 3A and Figure 3B schematically show the silhouette of the abrasive belt structure in a top view in accordance with preferred embodiments of the present invention; Figure 4 shows an example of a knitting pattern in accordance with a preferred embodiment of the present invention; Figure 5 shows another example of a knitting pattern in accordance with a preferred embodiment of the present invention; Figure 6 shows another example of a knitting pattern in accordance with a preferred embodiment of the present invention; Figure 7 shows another example of a knitting pattern in accordance with another embodiment of the present invention; Figure 8 shows an example of a reinforced knitting pattern in accordance with a preferred embodiment of the present invention; Figure 9 shows an example of a reinforced knitting pattern in accordance with a preferred embodiment of the present invention; Figure 10 shows another example of a reinforced knitting pattern in accordance with a preferred embodiment of the present invention; and Figures 11A through 11C show SEM images of cuts through grinding products.

[0078] the present description and the accompanying Figure Drawings are to be construed solely as schematic / diagrammatic representations and for exemplary and not limiting purposes, and the present invention is not limited to the illustrative preferred embodiments depicted therein. DESCRIPTION OF PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

[0079] In the following, preferred embodiments of the present invention are described in detail with reference to the accompanying Figure Drawings.

[0080] Figure 1 shows a section of an abrasive belt (1) in accordance with an embodiment of the present invention. The different layers that are shown in Figure 1 illustrate the abrasive belt (1) at different stages of its manufacturing process. As can be deduced from stage one, the textile fabric (2) of the abrasive belt (1) comprises a plurality of interconnected fabric strands (20). Preferably, the textile fabric (2) is in the form of a knitted textile fabric which can be produced on a textile making machine by warp knitting, for example. In stage two, the textile fabric (2) is physically fixed by applying an impregnation (30). In stage three, the impregnated textile fabric (2) was coated with a coating (40). Additionally, abrasive material or abrasives (50) was/were applied, optionally by using a suitable binding (binding) system.

[0081] As a result of this, a coherent abrasive area (60) is formed, wherein the abrasives (50) are evenly distributed over the (along the) abrasive belt (1). Stage three can be referred to as the final precursor stage before additional conversions and process stages are carried out to convert the material to a functional abrasive product. It is to be noted that impregnation is not mandatory and that the impregnation step can also be omitted. In addition, the abrasives can be directly applied on top of the textile fabric or impregnation, ie without any coating.

[0082] The type of interconnection between the fabric strands (20) is generally of lesser relevance as far as conflicting requirements as identified for abrasive belts can be fulfilled: combining a small elongation under load with an open structure and skill to achieve an even sanding result.

[0083] For this purpose, as can be deduced from the cross-sectional view in Figure 2, the number of crossings of the fabric yarns (20) at interconnecting points of the fabric yarns (20) is preferably uniform throughout. the textile fabric (2). Specifically, in Figure 2, the number of crossings of the fabric yarns (20) at interconnecting points is two.

[0084] This ensures that the local enrichment of the fabric yarns (20) due to the fact of the interconnections is limited. "Yarn enrichment" refers to the fact that in textile fabric (2), an interconnection of the fabric strands (20) is necessary in order to produce a coherent and physically stable material. Without interconnecting stitches only loose fabric yarns (20) should be produced, but no textile fabric (2) should be created. In theory and in practical terms, a warp knitting or other type of textile requires a minimum of one interconnecting stitch per stitch. When, however, more than two fabric strands (20) are crossing at such an interconnecting point, more than the minimum amount of fabric strands (20) for creating such an interconnecting point is present. Such yarn crossings involve more than two strands of fabric (20) per interconnecting stitch, therefore leading to lower elevations in the textile fabric (2) when the level of the interconnecting stitches is compared with the other parts of the textile fabric ( two).

[0085] The uniform number of crossings through the entire textile fabric (2) ensures a uniform height of the abrasive belt (1) which is preferably on the order of 1.5 times up to 5 times the diameter of the individual fabric yarns (20) . It is also not desired for certain surface areas to be on a lower level than other surfaces as this should result in uneven sanding results and the formation of streaks on the sanded surfaces.

[0086] Figure 3A and Figure 3B schematically show the silhouette of the abrasive belt structure in a top view. The silhouette of the abrasive belt (1) is therefore essentially identical for the abrasive area (60). As can be taken from this illustration, the openings (10) are highly symmetrical with respect to the machine direction (M1) and perpendicular thereto. This is preferable as such structures ensure that the abrasive regions between adjacent openings (10) are as uniform as possible, which in turn leads to a regularly and evenly distributed abrasive area (60) across the entire abrasive belt. (1). In other words, this means that the local abrasive area density, which can be measured in abrasive area per unit area, is essentially constant across the entire abrasive belt (1) (at least on unit area length scales, which are greater than or equal to the two opening diameters).

[0087] Furthermore, the openings (10) are arranged in lines (L1), (L2) perpendicular to the machine direction (M1) of the abrasive belt (1) and subsequent lines (L1), (L2) are misaligned one from the other with respect to the position of their openings (10).

[0088] Additionally, the width of the openings and the width of the region between two openings (i.e., the "connection region") are of the same order in transverse direction (i.e., in a perpendicular direction in the machine direction), the which additionally promotes a uniform sanding finish. For example, if the width of the openings is 1.5 mm, the width of the connecting region can be 0.3 mm to 5.0 mm, which still ensures sufficient “overlap” of the openings of subsequent rows. Even more preferable would be a connection region width which can be between 1 mm up to 2.0 mm for an opening width of 1.5 mm.

[0089] Strands or bundles (21) of interconnected fabric yarns (20), which separate neighboring openings (10), run at a certain angle with respect to the machine direction (M1). The term "bundles" of yarns shall refer to the overall configuration or direction that is described by the fabric yarns as they proceed through the textile fabric. Accordingly, the bundles (21) of fabric yarns (20) will form mirror images of each other observed from a plane crossing the connection points in the longitudinal direction of the abrasive belt (1) (Figure 3). Examples for similar opening geometries are shown in Figure 3A and Figure 3B, where Figure 3A shows essentially equilateral quadrilateral openings (10) and Figure 3B shows essentially hexagonal openings (10).

[0090] The uniformity of the abrasive area (60) for the symmetrical openings (10) that are illustrated in Figure 3A and Figure 3B can be further exemplified by a virtual projection of the abrasive area of two consecutive lines of openings (10) onto a perpendicular line to the machine direction, which will in both cases be highly uniform and will give a good “sanding area balance”. Consequently, the sanding area balance could be viewed as a measure for deviations in the physical area of the abrasive area within a repeat of the pattern, that is, within two consecutive lines (L1), (L2).

[0091] In this regard, the equilateral openings (10) can provide a sanding area balance that is even better as in the case of the hexagonal openings (10) if the machine direction is as indicated in Figure 3A and Figure 3B. Interconnection points between the unique hexagonal openings (10) should in that case be kept as short as possible in such a way that such areas will disturb the sanding area balance between the abrasive coated areas (50).

[0092] With respect to the bundles (21), the number of fabric strands (20) per bundle (21) is preferably two as this ensures a uniform thickness of the abrasive belt (1).

[0093] If the textile fabric is formed from knitted yarn, preferred knitting patterns are shown in Figure 4 and Figure 5. Another preferred knitting pattern is illustrated in Figure 6.

[0094] Turning first to Figure 4 and Figure 5, a possible structure is based on a textile fabric with binding (binding) of open atlas (Figure 4) or closed (Figure 5).

[0095] The term "open atlas binding" refers to a knitting pattern on a warp knitting machine that proceeds over (along) two or more rows. Thereby, the intermediate stitches between the stitches that induce a directional change can either be open, closed or a combination thereof. An open stitch pattern is, for example, based on the following type of warp knitting structure: 1-0/1-2/2-3/2-1// (Figure 4). As a result, the notation 1-0/1-2/2-3/2-1// is the notation in accordance with the ISO 8388:1998 standard (Page 76, “B4 Chain Notation”).

[0096] The term “closed atlas binding” refers as well to the intermediate stitches between directional changes in the knitting pattern. In contrast to the open atlas binding example, a closed atlas binding follows, for example, the following type of knitting structure: 0-1/2-1/3-2/1-2// (Figure 5) .

[0097] In the case of an atlas binding, the bundles (21) of interconnected wires (20) can generally be observed as protruding obliquely with respect to the machine direction (M1) of the abrasive belt (1).

[0098] Preferably, a two-tier atlas structure is used. In this respect, the number of rows refers to the number of stitches that proceed in one direction before the knitting proceeds in the opposite direction. Another definition is by reference to the repeated height of the pattern. In this case, the number of rows equals half the repeated height. For example, in the case of a repeated height of four atlases, the number of rows consequently equals two. In this context, the term "stroke" can be used which, in the field of warp knitting, refers to the number of stitches needed until the pattern that is to be knit begins to repeat itself. Consequently, a pattern having a repeat height of four requires four strokes until the next repetition begins.

[0099] Structures based on two rows provide openings (10) that are equilateral quadrilaterals. Accordingly, all surfaces located within the openings (10) in the textile fabric (2) have exactly the same area. This ensures an even distribution of the abrasive area across the entire abrasive belt (1). At the same time, the enrichment of the fabric threads (20) at the interconnecting points can be kept low. Furthermore, the openings (10) are arranged in lines (L1), (L2) perpendicular to the machine direction (M1) of the abrasive belt (1) and subsequent lines are offset from each other with respect to the position of its openings (10). Consequently, when used as an abrasive belt (1), such structures will provide an equal removal rate across the entire sanding surface integrity. In turn, the formation of stripes or similar structures on the workpiece can be avoided.

[00100] Furthermore, the openings (10) are stretched in the machine direction (M1), which is beneficial for the overall resistance of the textile fabric against stretching in the machine direction (M1).

[00101] Preferably, the binding direction is alternating for each needle. The binding proceeds in the same direction on every second needle in this structure, and it is also possible to use an atlas thread binding with more than two rows, such as three, four or more rows, but these structures are more prone to induce stripes on the workpiece.

[00102] As mentioned, another example for a preferred knitting pattern is the cord stitching shown in Figure 6. As a result, the cord stitching can form a mesh structure with similar quadrilateral openings (10) as in the previously mentioned two-row atlas structure (as shown in Figure 6).

[00103] Such a structure should follow a lapping pattern, for example, of the 1-0/2-3// type (Figure 6). Also this pattern will result in a structure having a low wire enrichment at the points of interconnection, such as the atlas binding previously described.

[00104] Structures with low enrichment of fabric yarns (20) like those shown in Figures 4 to 6 will as such enable the fabric yarns (20) to be as many as possible over a similar height level over the front and how much over the back of the textile fabric (2), which is preferable for many abrasive belt applications. In this case, the textile fabric front (2) will load the abrasive materials (50) and the textile fabric back (2) will support and distribute the pressure from the rear device as evenly as possible.

[00105] Also for the cord stitching, the openings (10) are highly symmetrical and the abrasive areas between adjacent openings are highly uniform across the entire abrasive belt (1). Furthermore, the adjacent openings (10) are offset with respect to each other in the machine direction (M1) of the abrasive belt (1). This will ensure a sanding result that does not cause streaks on the sanded article.

[00106] Although with atlas binding and cord stitching, two preferred knitting patterns have been described, it should be noted that the present invention is not limited to these structures. Other knitting patterns could also be suitable for achieving the desired properties in terms of mechanical stability, permeability of the belt to dust and other particles and a uniform sanding result. A further example is shown in Figure 7, in which a warp knitting structure of the type 10/12/10/12/23/45/43/45/43/32/21// is shown. This results in a more closed product with less dust extraction capacity, but with very high mechanical strength in machine direction. However, the sanding result could be more irregular when compared to the aforementioned structures.

[00107] Textile fabrics which are suitable in principle are defined in the ISO 8388 standard and comprise knitted weft fabrics (knitted) based on jersey, double layer knitted weft fabrics based on jersey, knitted weft fabrics based on flute, fabrics in weft knitted weft based, jersey based warp knitted warp fabrics, jersey based double layer knitted warp fabrics, rib based knitted warp fabrics, welt based knitted warp fabrics, knitted warp and weft combined fabrics jersey-based knits, and others.

[00108] It is also conceivable to transfer the patterns and configurations of the openings to other base materials, such as woven textile fabrics or even paper and film backings (films). Furthermore, it is also possible to manufacture structures with various filaments (weaves) to achieve different opening sizes and surface area proportions between the openings and abrasive areas.

[00109] In order to further promote the mechanical stability and in particular the resistance of the textile fabric (2) against stretching in the machine direction when tensioned it is preferable to integrate a tile (an inlay) of reinforcement or generally reinforcements for the belt abrasive (1). Preferably, these tiles consist of reinforcing wires (25) which are worked into the structure of the abrasive belt (1).

[00110] Preferably, a pillar stitch or a mosaic can be integrated as reinforcements in the machine direction. Figure 8 shows an example of a possible knitting structure that is reinforced by reinforcing yarn (25). As a result, the reinforcing threads (25) are shown in dark color. By way of example, the reinforcing threads (25) shown in Figure 8 are worked into a two-tier atlas binding. The resulting structure has predominantly quadrilateral openings with minimal thread enrichment at the connection points. The use of a pillar stitch for longitudinal reinforcement of the textile fabric leads to further yarn enrichment in this specific structure.

[00111] A preferred integration of a mosaic of reinforcement threads (25) for an atlas structure is to use an open or closed pillar stitch proceeding over (along) two rows as shown in Figure 8. In a In such a configuration, the 1-0/0-1// or 0-1/1-0// type reinforcement column point will protrude along the general direction of the atlas link and, consequently, will not lead to a partial coverage of the openings. In other words, the reinforcement threads generally follow the bundles of interconnected fabric threads. Such reinforcement is also worked for the basic stitch bonding in such a way that it is mechanically stitched to the basic textile fabric and, therefore, only allows for a certain limited stretch capacity (elasticity) (Figure 8).

[00112] Of course, the aforementioned atlas structure can also be reinforced in several different ways in order to reduce its elongation along the knitting direction of the textile fabric (2). Another example is shown in Figure 9, in which the atlas link of Figure 4 is reinforced by a mosaic link of 0-1/1-1//. In addition, in an atlas structure with a two-row net structure, open or closed stitches plus 0-0/0-0// mosaic are also suitable for reducing stretch along the knitting direction of the textile fabric. (two). However, such a type of reinforcement could lead to partial coverage of the openings in the textile. Another type of reinforcement is the incorporation of a 1-1/0-0 type mosaic that will follow the structure of the atlas link more closely.

[00113] Also for the cord connection, it is possible to integrate a pillar point in order to improve the mechanical properties of the material. An example is shown in Figure 10, in which a column stitch of type 1-0/0-1// or 0-1/1-0// is applied.

[00114] An alternative to using a pillar stitch is to use a mosaic strand that protrudes along the machine direction through the material and leads to a similar reinforcement as the pillar stitch reinforcement previously described.

[00115] Noteworthy, yarns that are either inserted as a mosaic, as a warp yarn or as a knitted pillar stitch lead to very low values of mechanical displacement when longitudinal forces are applied. The structure as described is nevertheless prone to stretch in the transverse direction. This circumstance can be used to control the size and configuration of the openings (10) in the textile fabric (2) during the impregnation process by stretching the textile fabric (2) and enabling the formation of larger openings or smaller openings (10) in the material.

[00116] The inserted knitting structure, mosaic threads or reinforcement threads (25) need to be sufficiently thin in order to avoid creating height differences in the final textile fabric surface and, at the same time, sufficiently strong to resist tensile forces.

[00117] Preferably, the reinforcing threads (25) have a maximum thickness of approximately 0.05 mm - 2.00 mm. More preferably, the thickness is in the range of 0.1mm - 0.5mm. In relation to the thickness of the fabric yarn (20) of the base textile fabric (2), a ratio of the thickness of the basic fabric yarn to the reinforcing yarn of approximately 1:1 to 20:1 is applicable in which a range 10:1 to 2:1 is in most cases preferred. With such a thickness for the reinforcement threads (25), it can be ensured that the uniform height distribution of the textile fabric (2) is not unduly affected by the integration of the reinforcement threads (25).

[00118] In this context, it should be noted that small height differences could be rebalanced in a later process step. This may include, for example, that during coating of abrasive articles, perhaps applicable printing technologies, such as screen printing, inkjet, gravure roller coating, and the like, in order to apply a coating of a style ( fashion) which enables the abrasive articles (50) to be spread in such a way that they only occupy a defined area of the textile fabric. In addition, the coated surface can be machined by an abrasion or sanding process to obtain a uniform surface finish. In such a way, a lack of quality in balance sanding area of the impregnated textile fabric structure can be compensated for during the coating process.

[00119] The same applies for an optional second coating (not shown) that is applied over the back of the belt. Accordingly, the second coating can be used for leveling the “back end” of the belt (ie, the part that does not come into contact with the workpiece).

[00120] The fabric yarns (20) for the textile fabric base (2) of the abrasive belts (1) and as well as the reinforcement yarns (25) are typically textured or flat yarns of polyester or polyamide due to the fact of its adequate tension properties and low costs. However, yarns based on natural fiber, such as cotton, hemp, or similar fiber, may also be suitable. This includes in more general terms the use of so-called chopped fiber (staple fiber) or multifilament yarns based on synthetic or natural fibers which can be used for the base structure or reinforcement of the textile fabric. Twisted yarns being single yarns or layered (worked) yarns can optionally also be used. Elastic yarns can be applicable in certain applications when the textile fabric must be stretched in a specific way, for example when a change in configuration of the openings to a special configuration is desired.

[00121] The term "textured yarn", commonly known as DTY (Drawn Texturized Yarn) (Drawn Textured Yarn), is a multifilament yarn that has been treated by thermal or mechanical methods or combinations thereof in such a way that the filaments of wire are spooled, shirred, or looped. There are various texturing methods that can be applied, such as air textured, knife edge texturing, false twist friction texturing, filler box texturing or shirred wire mesh.

[00122] The term “flat yarn” is commonly known under the abbreviation FDY, which is so called (Fully Drawn Yarn). Such FDY's can be of various types of construction based on mono- or multi-filament. These yarns can also be either glossy, semi-satin (semi dull) or completely satin (full dull) with respect to their appearance, which are the most common types. However, also various configurations of yarns, filaments and their cross sections are available which among others can be, for example, round, trilobal, multi-edge or any other type of configuration.

[00123] Yarns of both types, such as textured yarn or flat yarn, can irrespective of their type of texturing, or configuration and appearance additionally also be twisted. "Twist" refers to turning (turning) the yarn in two different directions that are commonly referred to as the "S" and "Z" directions. These twist directions only refer to the direction in which the yarns are twisted; in such a way that “S” and “Z” twisted wires resemble each other for mirror images. Such yarn twist has in most cases hardly any technical relevance in warp knitting, but leads to different optical effects in the final textile fabric.

[00124] The fabric yarn (20) for the basic textile fabric (2) and as well as the reinforcing yarns (25) can be monofilament yarns or multifilament yarns.

[00125] The term "mono filament yarn" refers to a man-made, endlessly spinning yarn that is constructed of a single filament of material. A yarn of a certain thickness such as 20 dtex is not separated into other substructures but consists of only one filament. A multifilament yarn consists of several substructures (filaments) in contrast to a monofilament yarn. Thereby, yarns can be distinguished by the number of filaments of which the yarn consists. As an example, a 20 dtex multifilament yarn can consist of, for example, two or more filaments.

[00126] A "layered (worked) yarn" typically consists of multifilament yarns, which can be twisted or untwisted yarns, textured or untextured yarns, and as well as woven or non-woven yarns. Whereas typically twisted yarns are not woven. These previously described single strands can then then be joined together to form a new, thicker, strand which is referred to as being layered (worked). Such a layered (worked) yarn, therefore, consists of at least two or more single yarns that are layered (worked) together.

[00127] The term “natural fibers” refers to fibers that have an origin from renewable sources. These refer to fiber-formed materials such as cotton, hemp, wood, silk or similar materials that are directly obtained from plants or animals.

[00128] The term "man-made fiber" is referenced to all fibers other than natural fibers. Man-made fibers can be synthetically produced from petrochemicals, bio-based polymers (biopolymers) or organic raw materials. Regenerated fibers are a subgroup under man-made fibers. These are made from natural materials such as plants by going through chemical and mechanical processes. These kinds of fibers are, for example, Viscose, Bamboo and Modal-type yarns which are made from cellulose. Synthetic fibers can be made from petrochemicals, eg polyester, vinyl acetate, nylon, aramid and carbon. This category also includes materials formed from chemically modified fiber and fibers manufactured from bio based building block polymers such as lactic acid, amino acids or propylene dioxide based materials.

[00129] Another important property of an abrasive belt (1) may be the electrical conductivity of the final abrasive product which may include the incorporation of carbon fibers or threads of similar materials that provide conductive properties. Examples of such modified wires are metal-coated wires or wires that have a conductive core or are treated with other treatments.

[00130] This does not exclude that the basic textile fabric (2) can still only be composed of carbon or other conductive yarns. In order to achieve a highly conductive material, this of course must also apply with respect to the resin used for impregnating the textile fabric. The resin may also contain conductive elements such as carbon, metals, metal ions and the like in order to achieve conductive properties of the textile-based composite and resin impregnation.

[00131] Examples of other potential yarns for textile-based belts include ultra high molecular weight polyethylene (UHMWPE) fibers, polypropylene [polypropylene (PP)] and aramid yarns. These can be used for the basic structure of the textile fabric or solely for the reinforcement of the material.

[00132] The thickness of flat or textured yarn can range from 5 dtex to 4,000 dtex, depending on the desired tension and elongation values of the textile fabric as a backing material, and the desired size of the abrasive grains or the end use of the final product. The “dtex” unit is by definition the weight in grams per 10,000 m of yarn. A typical thickness for atlas base yarn is between 150 dtex up to 900 dtex and between 15 dtex up to 450 dtex for reinforcement yarns.

[00133] When a knitted structure - even if reinforced by reinforcing yarns - is exposed to forces in the longitudinal direction, this can result in small, but still unwanted elongation. This can be avoided if the textile fabric (2) is already exposed to longitudinal stretching in time when the material is impregnated with a resin or coated with the coating or with the second coating preceding for the application of the abrasives. Due to the fact of this stretching of the textile fabric during impregnation, the mechanically displaceable parts are adjusted under tension. Consequently, the yarns are still under tension when the impregnation (30) / coating (40) is cured and the textile fabric (2) can better resist the longitudinal forces and additionally stretching is reduced.

[00134] Additionally, it is possible to control the stretching ability of the textile fabric (2) in a transverse direction after the final cure of the impregnation (30). Thereby, a more extensive stretching of the textile fabric (2) will lead to the formation of larger openings (10), but will also reduce the transverse elongation of the impregnated material after curing is complete. Such more extensive stretching during impregnation prevents the final textile fabric (2) from being stretched excessively in the transverse direction when the material is used as an abrasive belt, as during its use also transverse forces can occur (although the forces in the transverse direction are typically of significantly less magnitude than the forces occurring in the longitudinal direction).

[00135] Different types of impregnations (30) and coatings (40) can be applied to the textile fabric (2). The same applies for the second coat on the back of the abrasive belt. The types of resins used for impregnations and for coatings can consist of phenolic resin, urea resin or latex resin, as well as blends thereof, as described in European patent number EP 0,779,851. The abrasive belt can be coated using roller coating, spray coating, curtain coating, by printing methods such as screen printing or gravure rollers, transfer sheet or similar methods resulting in coatings referenced as a make-and-size-coat painting. Additionally, also radiation curable impregnation resins such as epoxides, acrylates, or similar resins can also be applied. Also thermally curable epoxides, acrylates, isocyanides or similar resins, and mixtures thereof, can be used for the mechanical stabilization of the textile fabric. Resins can include fillers (swellers) and additives such as surface active substances (surfactants) such as fatty acid ethoxylates, fillers or various species such as fibers, aluminum trihydroxide, kaolin, calcium carbonates, talc and the similar.

[00136] The textile fabric (2) of the abrasive belt (1) can additionally be subjected to any kind of surface modifications from the technique both of the front and the back of the textile as is also described in European patent number EP 0.779 .851.

[00137] The abrasive areas (60) can in the same process or in a separate process be spread or coated with abrasive articles (50), such as silicon carbide, aluminum oxide of various types or mixtures thereof, such as species and color brown, pink, white, or heat treated. Through this also high performance abrasives such as coated ceramic or similar grains as well as diamonds, CBN or other particles commonly referred to as super abrasives can be applied.

[00138] Figure 11A, Figure 11B and Figure 11C show SEM images of a cut through the cross section of the impregnated tissue. The cut runs perpendicular to the previously defined machine direction of the fabric and at the same time perpendicular to the front and back.

[00139] In the original SEM images (Figure 11A and Figure 11B), the fabric strands can easily be distinguished from the surrounding impregnation resin. Figure 11B shows a cross-section that was embedded for a "mold resin" (which is unrelated to the actual (actual) product and merely applied for imaging purposes) prior to cutting in order to achieve a planar cut and if it has the possibility to determine the area ratio between fabric yarns and surrounding impregnating resin by photographic analysis methods. The surrounding area of the mold resin is here taken into account and reduced from the total cross-sectional area.

[00140] In order to calculate the volume fraction ratio of the yarns and impregnating resin, the same analysis is performed on several repeated cuts (>5) in the machine direction in order to obtain a statistically relevant result.

[00141] The fibers are identified either manually or through an image recognition algorithm and the associated number of pixels is extracted (Figure 11C). The image for extracting the number of pixels from the wire area is shown in Figure 11C. A similar color or inverted color image (photo) is used to determine the area of pixels covered by the impregnating resin. The number of pixels from the wire surface is then related to the total number of pixels from the product's cut surface or to the number of pixels from the impregnating resin.

[00142] By calculating the average area fraction of the fabric yarns relative to the average fraction of the impregnating resin for a statistically sufficient number of cuts this can be taken as a volume ratio between the yarn and impregnating resin. In the example that is shown in Figures 11A through 11C, the volume fraction of fabric yarns to impregnation resin quantifies to about 1 - 7 and correspondingly the volume fraction of fabric yarns to the total volume of the product (excluding the openings) is about 0.6.

[00143] It is also possible to determine the weight fraction ratio of the fabric and the impregnated fabric by relating the weight of the fabric and the impregnated fabric after curing. This ratio remains between 0.05 and 0.9; while it preferably remains between 0.1 and 0.7; and even more preferably between 0.2 and 0.4. An abrasive belt with sufficient mechanical properties can be formed within these proportions.

[00144] At the same time, a certain amount of resin ensures that the irregularities arising from the textile fabric back (in terms of enrichment points of the fabric threads) can be balanced out.

[00145] Although, in the example above, a sample has been investigated in which only impregnation resin is present, the above analysis can equally well be applied for products that are (additionally) coated. In this case, the values are corresponding to volume/weight ratios of fabric yarn to resin where the resin fraction is then either formed by impregnating resin plus coating or merely coating.

[00146] In even more general terms, if additional components are present, the analysis above will lead to volume/weight ratios of the fabric yarns to the volume/weight of the product as a whole (not including the openings) and/ or for the applied coatings and combinations thereof.

[00147] The requirements for abrasive belts are demanding. The embodiments of the present invention described above allow for a homogeneous distribution of the grains as well as for proper dust removal and for sufficient tensile properties. Furthermore, the open structure is extremely useful in certain types of abrasive belt sanding machines where the transparency of the abrasive belt gives the machine operator a significantly better possibility to control the sanding process, as for example in the case of impact sanders.

[00148] Therefore, while the present invention has been described in accordance with specific examples and preferred embodiments, those skilled in the art will appreciate that the present invention can be embodied with a number of changes, modifications and variations while being conceivable without departure from the inventive spirit of the present invention, which is solely limited with regard to the scope of protection as set forth by the patent claims thereafter.

Claims (15)

1. Abrasive belt, comprising: a textile fabric being formed from interconnected fabric strands; and a coherent abrasive area that is a single, interconnected abrasive area that is continuous, and with which a work piece can be sanded or abraded; wherein the coherent abrasive area is formed on one side of the textile fabric; characterized in that: the abrasive belt further comprises a plurality of regularly distributed openings in the form of holes from side to side and has a uniform thickness; the openings are arranged in lines perpendicular to the machine direction of the abrasive belt; openings are regularly spaced in the line direction; and the lines are misaligned with respect to the position of their openings. 2. Abrasive belt, according to claim 1, characterized in that subsequent lines are misaligned with respect to the position of their openings. 3. Abrasive belt, according to claim 1 or 2, characterized in that the ratio of the volume of the fabric threads to the volume of the product as a whole, not including the openings, is from 0.1 to 0.9 and preferably from 0.4 to 0.8. 4. Abrasive belt according to any one of claims 1 to 3, characterized in that the coherent abrasive area on one side of the textile fabric comprises a coating applied to one side of the textile fabric. 5. Abrasive belt, according to any one of claims 1 to 4, characterized in that the thickness of the fabric threads is from 5 dtex to 4000 dtex and, in particular, from 150 dtex to 900 dtex. 6. Abrasive belt according to any one of claims 1 to 5, characterized in that the fabric threads are knitted (knitted), sewn or interwoven. 7. Abrasive belt, according to any one of claims 1 to 6, characterized in that the openings have the shape of an equilateral quadrilateral or are hexagonal in shape. 8. Abrasive belt according to any one of claims 1 to 7, characterized in that the openings have a long dimension and a short dimension, the long dimension extending in the machine direction of the abrasive belt and/or the largest diameter of the openings is from 0.3 mm to 20 mm. 9. Abrasive belt according to any one of claims 1 to 8, characterized in that the interconnected fabric strands are arranged in the form of bundles of a plurality of interconnected fabric strands, the bundles separating adjacent (neighbor) and openings being arranged so that they extend in a direction intercepting the machine direction and/or the number of fabric strands crossing at the interconnecting points of the interconnecting fabric strands is constant throughout the abrasive belt. 10. Abrasive belt, according to any one of claims 1 to 9, characterized in that the textile fabric has an atlas or cord structure. 11. Abrasive belt according to any one of claims 1 to 10, characterized in that it additionally comprises reinforcement threads worked into the textile fabric, preferably in which the reinforcement threads are worked into the textile fabric in the form of a pillar stitch , and/or preferably wherein the reinforcing threads have a thickness of 1 times to 1/20 times the thickness of the fabric threads and preferably 1/2 times to 1/10 times the thickness of the fabric threads. 12. Abrasive belt, according to any one of claims 1 to 11, characterized in that the reinforcement wires are worked in bundles. 13. Abrasive belt according to any one of claims 1 to 12, characterized in that the textile fabric is impregnated with an impregnation and the textile fabric is preferably tensioned during the application and/or curing of the impregnation. 14. Abrasive belt according to any one of claims 1 to 13, characterized in that the surface area of the openings is 0.1 times up to 10 times the total surface area of the total coherent abrasive area, preferably equal to or greater than the total surface area of the coherent abrasive area, and more preferably 1.0 times to 2.2 times the total surface area of the coherent abrasive area. 15. Abrasive belt according to any one of claims 1 to 14, characterized in that when a force of 100 N per 50 mm wide of a sample length of 200 mm is applied, the elongation is less than 1% and preferably less than 0.8%.

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